Embedded DRAM (eDRAM) is a capacitor-based dynamic random access memory integrated on the same die as an ASIC or processor. Embedding memory on an ASIC or a processor allows for higher operational speeds because low latency memory is on-chip, cutting delays due to wiring parasitics. Embedded DRAM also enables significantly larger bandwidth busses by virtue of removing the wiring bottleneck to off-chip memory systems. Also, larger amounts of memory can be installed on smaller chips to realize equivalent storage capacity using eDRAM since eDRAM has much higher density in comparison to SRAM. Although eDRAM requires additional fabrication process steps, the area savings of eDRAM memory offsets the additional process cost when a significant amount of memory is used in the design.
Factors such as parasitic resistance and capacitance in the trench capacitor can limit the performance of eDRAM cells. Various techniques can be used to mitigate these factors (e.g., reduce resistance by increased doping level), but these techniques can have limited effectiveness due to the high aspect ratio of the capacitor. For example, in one example, a trench can be formed in a substrate, and can undergo an anisotropic implant process to form a buried plate. Thereafter, an insulator layer and a polysilicon layer are deposited within the trench to form the capacitor. A transistor (gate) is then formed on the substrate, proximate to the capacitor; however, due to the capacitor formation processes, the resistive element (i.e., the polysilicon) of the capacitor connects to the diffusion region of the transistor, resulting in increased capacitor resistance. This increased access resistance, in turn, limits the switching performance of the capacitor.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.